1、字符串
NSString *mystring = [NSString stringwithFormat:@"the number is %D",3]
2、与C字符串相互转换
转C: [myString UTF8String]
或[myString cStringUsingEncoding:NSUTF8StringEncoding]
转NSString: [NSSting stringWithCString:"hekki" encoding:NSUTF8StringEncoding];
3、改变大小写
[myString uppercaseString]
[myString lowercaseStirng]
4、字符串提取数字
NSString *s = @"3.01";
[s intvalue],boolValue,floatValue,doubleValue